Storms wind down with showers through about midnight; cool but nice weekend ahead


Radar & lightning:Latest D.C. area radar shows movement of precipitation and lightning strikes over past two hours. Refresh page to update. Click here or on image to enlarge. Or see radar bigger on our Weather Wall.

8:20 p.m. update: We’re concluding our live blog as the threat of severe weather has ended across the area. With the front still sliding across from the west, showers continue in parts of the region through the hours around midnight (ending earliest west).

The weekend is looking pretty nice, as long as you don’t mind temperatures below normal. Saturday is partly to mostly sunny with highs near or a hair above 60. After overnight lows in the 30s to near 40 (maybe a frost or freeze north and west?) Saturday night, Sunday’s temperatures are probably a bit cooler, with highs mainly in the mid-and-upper 50s. Sunshine should still be abundant though. Winds may be gusty at times, particularly tonight as the front passes and on Saturday.

8:00 p.m. update: The tornado watch continues to get chipped away as the main line of concern pushes out over the bay and to the east. Only eastern sections remain under the watch and it’s likely to be dropped soon. A quick half inch or more of rain fell in the first batch many spots, with radar estimates past 1 inch in a few places.

In addition to the DCA wind gust over 50 mph, a report of a 70 mph gust has come in from Waldorf, Md. Other locations surpassing 50 mph include Upper Marlboro at 55 mph, La Plata at 53 mph and Huntingtown at 51 mph. The worst of the storms locally generally focused on the immediate DC area and south.

We may see a brief lull in spots, but additional showers are still possible until the front passes later this evening. It’s now pushing through Loudoun County.

7:30 p.m. update: The worst of the storms have pushed east of D.C. and are rapidly headed through the eastern suburbs. A wind gust of 53 mph was recorded at National Airport as the line blew through, with spotter reports of winds as high as 60 mph or higher in the area. Rain and thunder continues for a time behind the line, with additional activity possible as well as the cold front approaches from the west.

The tornado watch has been discontinued to the west of D.C., as any risk tends to wane behind the first line.

7:20 p.m. update: The tornado warning has been canceled early, but another severe t’storm warning has been issued for eastern DC as well as places to the east until 8:00 p.m. Wind gusts to 60 mph or higher are possible.

Storm relative velocity shows a rotating area of storminess to the south of D.C. after 7 p.m.

7:10 p.m. update: A Tornado WARNING has been issued for northern Charles County until 7:30 p.m. Some brief areas of rotation have shown up in the line, and this one tightened up for a while though it has weakened a bit since the warning went up. Locations in the path include Accokeek, Md.

Rainfall rates of up to and past 1″ per hour are also possible with this line as it moves through.

Overview, from 2:36 p;m.: The National Weather Service Storm Prediction Center has issued a tornado watch for the Washington, D.C. and Baltimore regions through 10 p.m. tonight.

The NWS cautions:

* SEVERAL TORNADOES POSSIBLE
* SEVERAL DAMAGING WIND GUSTS TO 70 MPH POSSIBLE
* A FEW LARGE HAIL EVENTS TO 1 INCH IN DIAMETER POSSIBLE

It also reminds us:

A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.

twIt’s important to stress a watch does not mean tornadoes are imminent or occurring, rather that the environment may support their development. If a WARNING is issued, on the other hand, it means radar is detecting a possible tornado or a tornado has been spotted, and you should seek shelter immediately.

The tornado watch in effect covers much of Virginia and central Maryland, and encompasses the District. This is not a classic tornado setup for the region, but there is enough turning of the wind with altitude that a few tornadoes could develop. They would probably be short-lived and small, but the characteristics of tornadoes are notoriously difficult to predict. Any/all tornado warnings should be taken seriously if issued.

Expected storm timing

Rogue storms could develop quickly throughout the region any time this afternoon. However, here is our best bet as to the timing of the most likely onset of storminess in different parts of the region:

3-4 p.m. Loudoun, Frederick and Fauquier counties
4-5 p.m. Stafford, Prince William, western Fairfax and western Montgomery counties
5-6 p.m. Inside the Beltway, the District, Howard, Prince George’s and Charles counties
6-7 p.m. Anne Arundel, Calvert, and St. Mary’s counties

The most solid line of storms with the heaviest rain is likely in the 6-10 p.m. timeframe throughout the region.

Rain should end between 1 and 3 a.m. from west to east.

Storm impacts

Here is what I see as the most and least likely storm impacts:

High likelihood: Heavy rain
Medium-high likelihood: Gusty winds
Medium-high likelihood: Thunder and lightning
Medium likelihood: Localized flash flooding
Low likelihood: Damaging winds and/or small hail
Low likelihood: Small, brief tornadoes
Very low likelihood: Large, long-lived tornadoes and/or large hail

Of all the impacts to be concerned about, heavy rain and flash flooding (mainly in low lying areas prone to flooding) rank highest on the list. One to 2 inches of rain in a short amount of time is possible.

Expired updates

7:05 p.m. update: Another severe t’storm warning has been issued for southern and southeastern parts of the area, including St Charles, Waldorf and La Plata until 7:45 p.m. for winds to 60 mph or greater.

Severe thunderstorms approaching the immediate D.C. area as of 6:50p.

Severe thunderstorms approaching the immediate D.C. area as of 6:50p.

6:50 p.m. update: Much of the immediate area is now under a severe thunderstorm warning until 7:30 p.m., focused on those within the Beltway as well as south and southwest. Winds in excess of 60 mph are possible with the line approaching the city. The worst of this line will move through fast, but you want to be indoors as it passes. Brief spinups are also possible though not expected to be widespread.

6:35 p.m. update: A new severe t’storm warning is up for southern parts of our area, including the city of Stafford, until 7:15 p.m. for destructive winds as high as 70 mph or greater. This warning includes parts of Charles, King George, Culpeper, Spotsylvania, Prince William, Stafford and Fauquier counties. No warnings in the area are currently active north of that zone, but moderate to heavy rain continues to advance east.

6:10 p.m. update: Rain, with spots of thunder, is advancing through western parts of the area now, with the front edge now passing places like Manassas to Dulles in Va. and Mount Airy in Md. At this time, the severe storms remain to the southwest with parts of our area under a warning for winds up to 60 mph+ till 6:45p. Those storms should at least clip the southern part of our region as they head east northeast. While rain, with embedded heavy activity, should roll east to the 95 corridor in the next hour, the strongest portion of the line may lag a bit.

Additional warnings (probably mainly for wind) are possible in the immediate area over the next few hours.

Regional radar, 5:30 p.m.

Regional radar, 5:30 p.m.

5:35 p.m. update: Heavy rain and embedded storms are closing in on the region from the southwest. We continue to think heavy rain and strong straight line winds are more likely in the D.C. area than tornadoes. Although some isolated showers are already popping up northeast of the District, the time of arrival for the main batch of storms is in the 6:00-7:30 p.m. timeframe for the D.C. area. The northern edge of this main batch is already extending into our far west and southwest suburbs. Severe thunderstorm warnings are currently in effect around Charlottesville into southern Madison and Green county until 6 p.m.

Some of the more violent weather is occurring in southern Virginia and northern North Carolina where several tornado warnings have been issued and there are some initial reports of damage (Blanks, Va. in Mecklenburg County).

4:50 p.m. update: Radar shows some nastier storms developing to the southwest and headed towards Charlottesville. The storms are coming up pretty quickly and should move into D.C.’s southwest suburbs by around 6 p.m. Right now, the main threat with storms coming in would appear to be some very gusty straight line winds and heavy rain, rather than tornadoes (though they cannot completely be ruled out and we would not be surprised to see a warning or two issued this evening).

twatches4:15 p.m. update: Amazingly, tornado watches extend all the way from central South Carolina to the Pennsylvania-New York border border. It should be noted that, throughout this region, the tornado risk is just marginal – meaning that while the environment could support a few tornadoes – a major tornado outbreak is unlikely. However, even if tornadoes don’t form, damage from straight line winds is possible (though not necessarily likely) when the brunt of the storms move through – most likely after 6 p.m.

This is a large, energetic weather system: the entire complex of storms extends from the Gulf Coast to Canada (link: national radar).

Regional radar at 3:40 p.m.

Regional radar at 3:40 p.m.

3:45 p.m. update: Regional radar shows the heaviest activity still well to the west and southwest in West Virginia and Southwest Va. Individual storms are moving from southwest to northeast as the whole complex of storms shifts east with the cold front. Per the information below, the period of heaviest, steadiest rain is expected to be here in the 6-10 p.m. window, but some front running storms are starting to develop in the mean time. Still no signs of anything severe, but we’re watching it.

3:10 p.m. update: So far radar does not show threatening weather – just a few showers rippling through northern Fauquier and western Loudoun counties. However, the environment is such that strong storms could develop rather quickly with little notice. Stay here for the latest updates.

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